Isolation of Sterols from Cowpea (Vigna sinensis) Seeds and Their Promotion Activity on HO-1

Abstract

Cowpea (Vigna sinensis K.) seeds were extracted with 80% aqueous methanol. Concentrated extracts were partitioned with ethyl acetate, butanol, and H2O, successively. The repeated silica gel and octadecyl silica gel (ODS) column chromatographic separations for the butanol fraction led to isolation of four sterols, whose chemical structures were determined as 7β-hydroxysitosterol (1), 7α-hydroxysitosterol (2), 7-ketositosterol (3), and stigmasterol 3-O-β-D-glucopyranoside (4) from the interpretation of spectroscopic data including NMR, mass spectroscopy, and infrared spectroscopy (IR). This paper reports the first isolation of compounds 1 and 2 from V. sinensis seeds. All compounds were evaluated for the effect on heme oxygenase-1 (HO-1) expression, which is considered to be an antioxidant enzyme that catabolizes heme into carbon monoxide, free iron, and biliverdin. All sterols increased the expression of HO-1 in HepG2 cells.